I hope your teacher set your task in writing. If so please post it exactly as it was given to you.

November 14th 2012, 06:22 AM

Tweety

Re: complex numbers, help

Okay,

1) Z is the complex number

a) State the value of , hence show that for all
b) use the formula for the sum of a geometric series to show that
c) Let show that . Also show that and hence find an expression for in surd form.

i have done all parts except part c, am stuck on that bit

my solutons for a and b

recognising z as an 5th root of unity?

b)

November 14th 2012, 06:48 AM

Plato

Re: complex numbers, help

Quote:

Originally Posted by Tweety

Okay,
1) Z is the complex number
c) Let show that . Also show that and hence find an expression for in surd form.

I think that I have written this before. But again, posting the complete problem to begin with saves a lot of time.

Let us use a more convenient notation..

Here are useful facts for any nonzero complex number .
If then and

Now try the question.

November 14th 2012, 09:06 AM

a tutor

Re: complex numbers, help

In post 2 I meant it's NOT true for all z.

Sorry.

November 14th 2012, 09:36 AM

Tweety

Re: complex numbers, help

i am actually stil not able to compute part 'c'

November 14th 2012, 09:59 AM

Plato

Re: complex numbers, help

Quote:

Originally Posted by Tweety

i am actually stil not able to compute part 'c'

If can't you show that

November 14th 2012, 10:34 AM

Tweety

Re: complex numbers, help

Quote:

Originally Posted by Plato

If can't you show that

BUt I dont understand how alpha equals that ?

November 14th 2012, 10:50 AM

Plato

Re: complex numbers, help

Quote:

Originally Posted by Tweety

BUt I dont understand how alpha equals that ?

I posted it above.
If then and

Recall that is an even function and is an odd function.

November 14th 2012, 11:56 AM

mathteacher067

Re: complex numbers, help

Hello!
Would try to help you!
I'm not sure, but what i got is
Rectangualr form a^2*z^2+1/z^2+2
Polar form a^2*z^2+1/z^2+2
check it here Online Complex Numbers Calculator
I used Complex Numbers Calculator
Good luck